Tunisian knit stitch
The hook enters between the front and back vertical bars, giving a knitted-looking V.
Counted practice swatch
Make a 15-loop Tunisian foundation and complete its return pass.
Work the repeat
Forward: skip the first edge; insert through the fabric between the front and back bars of each stitch and pull up a loop. At the last edge insert through both edge loops. Return: yarn over through one, then through two repeatedly.
Read the fabric
Entering only the front bar makes Tunisian simple stitch instead. Keep the forward loops loose; dense Tunisian knit fabric curls and needs a suitably long hook.